DNA repair is a natural response of living organisms that face various forms of physical or environmental insults. Both prokaryotes and eukaryotes have developed multiple pathways to repair DNA damage (1). These pathways constitute specific biochemical reactions catalyzed by a large number of cellular proteins. These proteins participate in one or more of the three basic steps of DNA repair, namely, i) damage recognition ii) damage removal and iii) reconstitution of the DNA sequence. Recent studies using different unicellular and multicellular organisms have shown that many of the components of these pathways are conserved throughout evolution (1). Furthermore, many of these proteins appear to be involved in more than one pathway (2). This is achieved by virtue of the ability of these proteins to selectively interact with other proteins involved in DNA metabolism. Thus, many proteins involved in DNA repair are also involved in DNA recombination, replication or transcription and vice versa (3-5). It is believed that this selectivity in the interacting with `right` partners allows these proteins to regulate these intricate biochemical reactions.
A previously reported repair protein from Drosophila melanogaster (6) was shown to be an endonuclease that specifically cleaved the phosphodiester bond 5' to an apurinic or apyrimidinic site (hence the name AP endonuclease; ref. 6). Another Drosophila protein of this class is believed to take part in recombination and repair (8).
Thus, many repair proteins exhibiting multiple functions themselves also interact with different proteins to take part in various biological processes such as DNA recombination, replication and transcription (3-5).
The maize repair protein orthologue-l polynucleotide of the present invention shows a high sequence identity to the previously reported repair protein from Drosophila melanogaster (6). The maize repair protein orthologue-1 polynucleotide of the present invention, however, is the first repair protein orthologue reported to exist in a multicellular plant.
Control of DNA recombination, replication, and transcription provides the means to modulate the efficiency of heterologous nucleic acid incorporation into the genomes of a target plant cell. Control of these processes has important implications in the creation of novel recombinantly engineered crops such as maize. The present invention provides this and other advantages.